This invention relates to fiber optic networks, and particularly to WDM optical networks.
The public's increasing demand for bandwidth has accelerated the interest in wavelength division multiplexing (WDM) technology. Using WDM, data can be transmitted at high rates on each of several wavelengths of light, sharing a single optical fiber. Currently, systems exist in which a fiber carries over 100 Gb/s of data using 40 or more wavelengths. Conventionally, individual optical channels are “dropped” by inserting a filter in the main fiber path. The filter diverts, and thus effectively extracts, a given wavelength to a separate port that, often, is connected to equipment that demodulates the diverted optical signal to recover data that had previously modulated an optical signal at that given wavelength. Similarly, the addition of an optical channel is typically achieved by the insertion of a filter in the main fiber path, which filter injects light arriving at the node at a desired wavelength into the main optical path. When multiple wavelengths are to be dropped or added, either multiple optical filters must be inserted in the main optical path at the location of the node, or a multi-wavelength multiplexer/demultiplexer is used.
An effective design approach is needed for efficient utilization of optical fiber capacity.